TACOMA, Wash. — A decorated Air Force Reserve flight nurse discharged for being gay took the witness stand at her federal trial Monday and told the judge it "kills me" not to be able to care for wounded soldiers while the country is at war.

Former Maj. Margaret Witt has sued the Air Force in hopes of being reinstated.

No one in her unit or any of her patients ever expressed concern about her sexual orientation, she told the judge.

"It's what I've spent over half my life training to do," Witt testified, her voice breaking. "I miss being able to be the one that that soldier looks at and I can do something for him. I'm not complete, and it kills me to not be there."

The case has been closely watched by those on both sides of the gay rights debate.

Proponents believe another big legal victory would build momentum for a congressional repeal of "don't ask, don't tell," the 1993 law that prohibits the military from asking about the sexual orientation of service members but requires discharge of those who acknowledge being gay or are found to engage in homosexual activity.

Earlier this month, a federal judge in California ruled that "don't ask, don't tell" violates the due process and free speech rights of service members. That opinion has no direct bearing on Witt's case.

Witt joined the Air Force in 1987 and later became a flight nurse, helping to care for and evacuate soldiers wounded in Afghanistan. She was suspended in 2004 when the Air Force investigated her for violating "don't ask, don't tell." She was discharged three years later, while just short of becoming eligible for a full pension.

Her lawsuit challenged the constitutionality of "don't ask, don't tell." In 2008, a three-judge panel of the 9th U.S. Circuit Court of Appeals considering the case held that the military couldn't discharge someone for being gay unless it demonstrated the firing was necessary to further military goals.

The case returned to U.S. District Court in Tacoma, where Judge Ronald B. Leighton must determine whether Witt's firing met that standard. Leighton heard testimony last week from several of Witt's former colleagues, who said they didn't care about her orientation and that her firing actually hurt morale in their squadron, based at what is now Joint Base Lewis-McChord near Tacoma.

The Air Force maintains that Witt's firing was justified, and the appeals court ruling was out of line with 9th Circuit and Supreme Court precedent.

In pointed cross-examination, Justice Department lawyer Peter Phipps noted Monday that Witt had engaged in an adulterous relationship with a married civilian woman in 2003. The woman, now divorced, is still Witt's partner, but the Air Force argues that Witt's disregard for policy in committing adultery set a bad example for others in the unit and justifies her dismissal.

"You agree that adultery is not consistent with high standards of integrity, correct?" Phipps asked.

"Yes," Witt responded.

The government also argues that Witt acknowledged being homosexual to some of her close friends in the unit, forcing them to choose between loyalty to her and to Air Force policy. Her firing eliminated a risk to unit cohesion, a legitimate military goal, DOJ lawyers say.

Witt's attorneys insist that the government has no evidence proving Witt's firing was necessary to further any military goal. In fact, they argue, there's no evidence that allowing gays to serve openly would hurt unit cohesion, or even any evidence that troops perform better if they get along socially.

Elizabeth Kier, a University of Washington associate professor of political science who has studied the issue, followed Witt on the stand Monday. She summarized research in the field thusly: "There is no significant positive relationship between social cohesion and performance, and high levels of social cohesion can undermine military effectiveness."

Closing arguments are expected by Wednesday. It is not clear when Leighton will rule.